1. On behalf of the LHCb collaboration
Sergey Barsuk
CERN and ITEP,Moscow
Assisi, June 20–24, 2005
On behalf of the LHCb collaboration
The LHCb experiment:
Status and expected physics
performance

2. Introduction
LHCb is a dedicated experiment to study CP violation and other rare phenomena in B meson decays (and also c,τ,jets,…):
Precision measurement of CKM parameters;
Test of Standard Model predictions / search for new physics
Expect ~1012 b-hadrons / year
All b-species are produced: Bu (~40%), Bd (~40%), Bs (~10%), Bc (~0.1%), Λb (~10%), … , Excited states, …
Bu, Bd are being explored in great detail (thanks to B-factories)
=> Improve statistics (other sources of systematics)
Bs time resolved studies (not accessible at B-factories)

3. b-production at LHCb θb LHC Luminosity @ LHCb: 2-5 x 1032 cm-2s-1
σbbar = 500 μb
σinelastic = 80 mb
beam θb
1 LHCb year = 2 fb-1 = 1012 bb

4. Detector requirements
Example:
Decay: Bs -> Ds K, Ds -> Φπ
Flavour tag: B -> Dlν B Bs K π e ν D Ds
PVx
SVx
Exclusive B-decay reconstruction
=> Kinematics measurement
=> Particle ID
Flavour tagging
=> Particle ID
Proper time (L~1cm)
Fast Bs oscillations
=> Precise vertexing
+ Efficient trigger
+ Control of systematics

5. ->Talk by Matthew Needham
The LHCb detector: kinematic measurements
Charged tracks
γ, πo
Vertex LOcator
Trigger Tracker
Inner/Outer Tracker
Magnet
Calorimeter
->Talk by Matthew Needham

6. Vacuum vessel arrived at NIKHEF in 04/2005
VErtex LOcator
21 stations in vacuum tank
R/φ sensors
~180k R-O channels
VELO
Si sensor
1 m
Sensors sensitive area
8mm from beam line
(30 mm during injection)
hybrid
R-O chip
PVx position resolution:
x,y: ~ 8 μm
z: ~ 44 μm
IP precision: ~ 30 μm
VELO in the TestBeam in 2006
-> study of pattern recognition, alignment, …
Vacuum vessel arrived at NIKHEF in 04/2005

7. Installed and commissioned in 2004
Magnet
∫Bdl = 4 Tm
Warm dipole magnet (Al), Fe yoke = 1600 t
Daily reverse field to reduce systematics
Installed and commissioned in 2004
Field mapping ongoing

8. Tracker T1-3 OT TT IT Sensors Kapton cable Trigger Tracker
Silicon Strip, 1.6 x 1.3 m2
=> 144k channels
Inner Tracker
Silicon Strip, 1.2 x 0.6 m2
=> 129k channels
Outer Tracker
Straw tubes, 5.6 x 4.6 m2
=> 54k channels
Sensor ladders
60% of chambers produced
Electronics hybrid
Efficiency ~94% (p>10 GeV/c)
Ghost rate ~3% (pT>0.5 GeV/c)
Momentum resolution ~0.4%

9. ->Talk by Tito Bellunato
The LHCb detector: particle ID
π/K/p
e, γ, πo μ
RICH system
Calorimeter
μ -system
->Talk by Tito Bellunato

10. RICH system RICH1: Aerogel and C4F10 RICH2: CF4
mrad
RICH1
mrad
RICH1: Aerogel and C4F10
RICH2: CF4
π/K separation for true pions from B->ππ events
<π/K separation>
Photon detectors: Hybrid PhotoDiodes (HPD)

11. RICH system Contract for 500 HPDs signed
Delivery starting from 07/2005
Installation of RICH1 shielding in the LHCb detector
Entrance/exit windows of RICH2

12. Calorimeter Scintillator Pad Detector / Preshower (SPD/PS)
Electromagnetic calorimeter (ECAL)
Hadronic calorimeter (HCAL)
projective geometry,
variable granularity
SPD/PS
SPD/PS
Sc-Pb-Sc 15mm-14mm-15mm
2 x 6k detector cells/R-O channels
Deep groove design of cell
2.5 Xo depth
Production ongoing
HCAL
ECAL
SPD/PS modules with 144, 64 and 16 detector cells
100% outer type modules produced

13. Lateral scan of ECAL module with 50 GeV e-beam
Calorimeter: ECAL
Shashlyk technology
6k detector cells/R-O channels
Volume ratio Pb:Sc = 2:4 (mm)
25 Xo , 1.1 λ depth
Production completed
Light yield: ~3000 ph.e./GeV
Cell-to-cell spread: r.m.s.<7%
Energy resolution: σ(E)/E = 10%/VE + 1%
Lateral scan of ECAL module with 50 GeV e-beam
ADC channels
Spread across the module:
for beam parallel to module axis: < ±1.3%
for beam at 200 mrad: < ±0.6% mm X

14. Calorimeter: ECAL
Wall size is within measurement error to design value
x,y-positions of module are known to ±0.5 mm
z-position: all modules within ±2 mm

15. Calorimeter: HCAL Fe-Scintillator tile calorimeter
1.5k detector cells/R-O channels
5.6 λ depth
Production completed
Cell-to-cell spread: r.m.s. < 5%
Assembly of HCAL module
1/2 HCAL is installed in the detector

16. Muon detector 5 stations with projective pad R-O Production at 6 sites
In total: 1368 MWPCs
Produced and tested: 450 MWPCs (~30%)
PNPI2
Poliuretanic foam
Cathode PCB
Cathode pads
20 ns
Efficiency ~95%
π-misID rate <1%
2mm pitch wire R-O

17. A very busy time in the LHCb cavern

18. Trigger -> talk by Frederic Teubert Level 0 (40 MHz -> 1 MHz)
-> hardware
high-pT e, γ, πo, μ, h
=> CALO, MUON
pile-up veto
=> VELO
Level 1 (1 MHz -> 40 kHz)
-> software
large IP and pT tracks
=> VELO, TT
High Level Trigger
complete event info
=> ALL
~offline selection
-> 2 kHz on tape
-> systematics and data mining
Large pT
b-physics topology
Mb ~ 5 GeV/c2
βγcτ ~ 1 cm
Large IP L0 L1
L0xL1

19. Baseline measurements
Bs oscillations frequency, phase and ΔΓs
Bs -> Ds π
Bs -> J/Ψ Φ, J/Ψ η, Φ ηc
Measurement of γ=-Arg Vub
Bs -> Ds K
only tree diagrams -> no NP
Bd -> ππ, Bs -> KK
U-spin symmetry, NP in gluonic penguins
Bd -> Do K*, Do K*, DCP K*
Dunietz-Gronau-Wyler method, NP in DD-mixing
Rare decays, search for NP
Bd -> K*γ, ωγ, Bs -> Φ γ
Bs -> ΦΦ, Bd -> ΦKs
Bd -> K* μμ
Bs -> μμ

20. Event generator: Pythia+QQ
Full detailed Geant simulation of detector
pile-up and spill-over included
Realistic digitization and reconstruction with full pattern recognition
Realistic L0, L1 trigger simulation
Assumption: Major background:
bb-inclusive events
large pT, IP, secondary vertices, multiplicity
Toy MC used for sensitivity studies
acceptance and resolutions parameterized from full MC
Reconstruction/analysis software environment
-> talk by Patrick Koppenburg

21. Δms measurement: Bs -> Dsπ
Ds -> KKπ
Proper time resolution ~40 fs
LHCb 1 year
Δms = 25 ps-1
82k events/year
B/S = 0.32 ± 0.10
5σ measurement in 1 year of running for Δms up to 68 ps-1
(far beyond Standard Model expectation Δms < 26 ps-1)
Once oscillations are established, determine Δms with σ(Δms) ~ 0.01stat ps-1

22. γ measurement: Bs -> DsK
Ds -> KKπ
K/π !!!
5.4k events/year
B/S < 1
Bs -> Dsπ
Bs -> DsK
Measures γ-2χ
5 LHCb years
Bs -> DsK
1 LHCb year
Bs -> Dsπ
Δms, (ps-1 ) 20 25 30
σ(γ), (o)
14.2
16.2
18.3

23. Bd -> ππ, Bs -> KK
Bd -> ππ
Bs -> KK
K/π !!!

24. γ measurement: Bd -> ππ, Bs -> KK
Measures γ
Time-dependent asymmetries for Bd->ππ and Bs->KK:
ACP(t) = Adir cos(Δm t) + Amix sin(Δm t)
Parameters: γ, φd(φs), P/T = d e iθ
Take φd(φs) from other measurements
U-spin symmetry [Fleischer]:
dππ = dKK and θππ = θKK
=> 4 measurements, 3 unknown
=> Solve for γ
σ(γ) ~ 5o in 1 LHCb year
Uncertainty from U-spin assumption
Sensitive to new physics in penguins
Bd -> ππ 25k events/year
Bs -> KK 37k events/year
LHCb 1 year
Contours
68% CL
95% CL

25. Bs -> J/Ψ Φ J/Ψ -> ll Φ -> KK
Non-CP state => partial waves
Measures φs = -2 χ; χ~0.02 is small
Simultaneous measurement of ΔΓs; in SM ΔΓs/Γs~0.1
Annual yield
B/S
100k
< 0.3 7k
< 5.1
3.2k
< 1.4
=> 5 years sensitivity σ(φs)~0.02

26. Test of SM/QCD; search for NP
Rare decays
Test of SM/QCD; search for NP
Bs -> Φγ
Bs -> ΦΦ
Gluonic penguin
E/W penguin
9.3k events/year
B/S < 2.4
1.2k events/year
B/S < 0.2
Bs -> μμ
Bd -> K*μμ
E/W penguin
LHCb 5 years
4.4k events/year
AFB
~17 events/year

27. Bc -> J/Ψ π LHCb ~1.5 month CDF 2005 Yield: 14k events/year
B/S < 0.8

28. Flavour Tagging SVx PVx
Determine the flavour of the signal B-meson at production
Quality of the flavour tagging
tagging efficiency εtag = (R+W) / (R+W+U)
wrong tag fraction ω = W / (R+W)
effective tagging efficiency εeff = εtag (1-2ω)2
(after passing trigger and offline cuts) Bs Bo D l- K- K+
Qvx
PVx
SVx
Algorithms
“Opposite side”
leptons from semileptonic decays
K± from b->c->s chain
inclusive vertex charge
“Same side”
K± from fragmentation accompanying Bs meson
In the LHCb, measure ω using control channels with similar topology

29. Summary of principal physics channels
Nominal year = 1012 bb pairs produced (107 s at L=2x1032 cm-2s-1 with σbb=500μb)
Yields include factor 2 from CP-conjugated decays
Branching ratios from PDG or SM predictions

30. Performance after 1 LHCb year (2 fb-1)
channel
yield
precision γ
Bs -> Ds K
Bd -> ππ, Bs -> KK
Bd -> Do K*
Bd -> DCP K*
5.4k
26k, 37k
0.5k
3.4k
0.6k
σ(γ) ≈ 14o
σ(γ) ≈ 6o
σ(γ) ≈ 8o χ
Bs -> J/Ψ Φ
120k
σ(χ) ≈ 2o
|Vtd/Vts|
Bs -> Ds π
80k
Δms up to 68 ps-1
rare decays
Bd -> K* γ
35k
σ(ACPdir) ≈ 0.01
+ systematics !
-> talk by Guy Wilkinson

31. Summary
LHCb detector is optimized for precise measurement of CP violation and search for new phenomena
Exploit ~1012 b-hadrons / year with all b-species
-> B(s,c)-factory
Complementary/competitive to (Super)-B(d,u)-factories and Tevatron
Detector construction is advancing well
To be ready for the first LHC collisions in 2007
Physics potential can be fully exploited with the initial LHC luminosity
More on LHCb in Wednesday/Thursday talks:
-> M.Needham “Status of the LHCb tracking system”
-> T.Bellunato “Status of LHCb RICH and HPD”
-> F.Teubert “LHCb trigger development”
-> G.Wilkinson “LHCb strategy to understand systematics”
-> P.Koppenburg “Reconstruction and analysis software environment of LHCb”

32. To conclude …
Historically, competitions on Beauty involve the famous apple …
… the Apple of Discord

33. … and in a few years … NP